The present invention relates to improvements in the field of tire recycling. More particularly, the invention is directed to the recovery of commercially valuable products from used rubber tires.
Tire recycling has become a necessity because of the accumulation of large quantities of scrap tires which represents a major environmental problem. Each year, about 24 million used rubber tires are disposed of in Canada and about 250 million in the United States. While some of these tires are recapped or ground up for special uses, most are simply dumped in rural farm land or in landfill sights. When buried in landfills they eventually float to the surface, and when piled the non-biodegradable rubber will cause serious damage if ignited by lightning or vandals.
On the other hand, used rubber tires represent a source of energy and raw products for the production of rubber parts. By thermal decomposition of rubber, it is possible to recover to a certain extent the initial ingredients which constitute a tire. To this end, Applicant has already proposed in U.S. Pat. No. 4,740,270 a process for the treatment of used rubber tires by vacuum pyrolysis in a reactor to produce liquid and gaseous hydrocarbons and a solid carbonaceous material. According to this process, the pyrolysis of the tires is carried out at a temperature in the range of about 360.degree. C. to about 415.degree. C., under a subatmospheric pressure of less than about 35 mm Hg and such that gases and vapors produced in the reactor have a residence time of the order of a few seconds. As a result, pyrolytic oils are obtained in substantially maximum yield. Typically, about 60 weight % hydrocarbon oils, about 38 weight % solid carbonaceous material and about 2 weight % gaseous hydrocarbons can be produced by such a process. As indicated in Applicant's aforementioned patent, the hydrocarbon oils produced have a calorific value of about 10,200 kcal kg.sup.-1 and are thus suitable for use as heating fuel. However, it would be desirable to increase the value of these pyrolytic oils with a view to obtaining commercially valuable chemicals.